Propellant powder



Patented Apr. 11, 1944 trap is ATES PATENT orrice PROPELLANT POWDER Ellsworth S. Goodyear, Kenvil, N. 3., assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware i No Drawing. Application August 9, 1940,

Serial No. 351,961

'7 Claims.

This invention relates to an improved propellant smokeless powder and more particularl to a novel and improved method of producing a high gravim'etric density, free flowing, non-clustering, progressive burning smokeless powder.

Heretofore the art has recognized and used surface coated propellant powder. The surface coated propellant powder which the art has pro- The methods of coating smokeless powder with v deterrent materials now used comprises, in general, the tumbling or stirring of powder grains in the presence of a quantity of deterrent material. The tumbling v,or stirring process is normally carried out in a revolving drum or sweetie barre and the coating processes now used are aided by the addition to the drum of solvents or By this invention, smokeless powder is coated with the same class of deterrent materials as used by the prior art, but in such a way as to obtain uniform distribution and ample penetration of the deterrent material in a reasonable time and without stickiness and with much less clustering. Further the process of this invention produces powder having a high gravimetric density and excellent ballistics. According to this invention, smokeless powder is wet with a volatile liquid which is a non-solvent or a poor solvent for the smokeless powder and is a poor non-solvents for the powder grains and coating materials.

However, in each of the above described methods of prior art in which the powder grains do not finally receive a substantially equal concentration of the deterrent material on. all of the grain surfaces, because ofthis unequal distribution, high gravimetric densities are not obtained and uniform ballistics are difficult to maintain. The grains also tend to be more or less sticky and form clusters and thus do not load freel into the cartridges. This clustering is mainly due to the lack of a uniform coating on the grains.

It is the object of this invention to produce a propellant smokeless powder which has a substantially equal coating of deterrent deposited on all surfaces of the individual powder grains.

A further object of this invention is to provide an improved means of surface coating progressive-burning smokeless powder.

Av further object of this invention is to produce a smokeless powder with an increased gravimetric density, better free flowing characteristics and more regular ballistics.

A still further object provide a propellant smokeless powder which will give standard ballistics with a lower weight of charge. Other objects will appear hereinafter.

of this invention is tosolvent for the deterrent materials. To the powder so wet, is added a finely ground deterrent. material, which is only weakly soluble in the volatile liquid, and the mass tumbled together at elevated temperatures. The temperatures may be below or above the meltin point of the deterrent material, .but it has been found advisable when nearingthe end of the coating process to raise the temperature of the powder to a point above the melting point of the deterrent material for a short time.

The volatile vehicle is so selected that it is a weak solvent for the deterrent and thus serves as a transfer medium dissolving small quantities of the deterrent material and then giving it up to the powder. Because of the low solubility of the deterrent material in the volatile vehicle, the concentration being deposited on the grains ,is never high enough to cause stickiness and the deterrent material penetrates into the grain as fast as the volatile vehicle allow its disposition. Tlie volatile vehicles which are suitable in accordance with this invention are ethyl alcohol, .dioxane,. acetone, petroleum naphtha, butyl acetate and the like either alone or in admixture with each other or water. The most suitable mixtures being ethyl alcohol-water, acetone water, dioxane-water and petroleum naphtha-butyl acetate. The composition of the mixture is determined by th solubilit of the specific deterrent to be used. Deterrent ma be for example, dimethyldiphenylurea, diethyldiphenylurea, dinitro-toluene, ethyl drtho benzoyl benzoate, tri-' phenylphosphate, on similar substances or mix- Exams: 1

As a basis of comparison, 1812 parts by weight of uncoated double base tubular rifle powder containing 20% nitroglycerin was coated by a prior art method which comprises wetting the powder with a solution containing 100 parts by weight of Centralite (symmetrical diethyldiphenylurea) dissolved in 181 parts by weight of ethyl alcohol. The wetted powder was revolved in.,a sweetie barrel for onehourat a temperature of 85 C., after which, the powder grains were dried, glazed, screened and humidified. The powder so manufactured gave a 60% yield of unclustered grains which had a gravimetric density of .941 and which when tested in a .50 caliber rifle with a charge of 243 grains gave velocity of 2833 ft. per second with a pressure of 46,700 pounds per sq. inch.

EXAMPLE 2 To show the improvement obtained by using the process of this invention for coating, 1812 parts by weight of the uncoated double base t'ubular rifle powder grains such as was treated in Example 1 were placed in a sweetie barrel wet with 182 parts by weight of a 2:1 alcohol,

unclustered grains was obtained which had a gravimetric density of .950 and which when tested in a .50 caliber rifle with a charge of 255 grains gave a velocity of 2830 ft. per second and a pressure of 46,300pounds per sq. in. It will benoted that the yield of unclustered grains has been increased by V4 and substantially the same ballistics were obtained.

Exmu: 3

A sample of uncoated powder grains was coated by a prior art method which comprises coating 50 parts by weight of tubular rifle powder with ,4 parts by weight of water and 1.25 parts by weight of ethyl ortho benzoyl benzoate. The

coating was applied by revolving the sweetie barrel for 45 minutes at a temperature of 65 C.,

- material was revolved in a barrel and 100 parts by weight of ethyl ortho benzoyl benzoate wereadded. The barrel was revolved for one hour at a temperature of 65C. and the deterrent was gradually dissolved and deposited on the grains.

The powder was dried, glazed. screened, and humidified. From this example, a yield of 98.5% unclustered grains having a gravimetric density of 1.007 was obtained.v When tested in a .50

10, caliber rifle, a charge of 263 grains gave a velocity of 2792 it. per second and a pressure of 40,600 pounds per sq. in. I

It will be noted that the powders of Examplesv 3 and 4 which were coated with ethyl ortho benzoyl l5 benzoate definitely prove that the method of coating in accordance with this invention gives a higher gravimetric, density and allows higher velocities with reduced pressures to be obtained.

Exmu: 5

thereto the deterrent material in a solution and tumbling the mass forone hour at 65 C. The solution consisted of 120 parts by weight of triphenyl phosphate -in 181 parts by weight 0;. water.

The powder was removed from the barrel, dried,

glazed, screened, humidified and tested. The

gravimetric density of the powder was .848.

Exmrn 6 To show the improvement possible over the 'results given in Example 5, a powder was prepared in accordance with this invention by coating 1812 parts by weight of the uncoated powder grains of Example 5 by wetting the material with 181 parts by weight of an alcohol-water (125-56) 40 mixture and 120 parts by weight of triphenyl phosphate added. The barrel was revolved tor one hour at 65 C. and the powder finished as in Example 5. The alcohol-water mixture is a poor 'solvent for the triphenyl phosphate and allows a slow transfer to the powder grains. The gravipreceding examples has been applied to double after which, two parts by weight of additional water and .875 part byweight of additional ethyl ortho benzoyl benzoate were added. Thedrum was revolved an additional 50 minutes at (3. and then 2 parts of additional waterv and .265

partadditional ethyl ortho benzoyl benzoate were To show the improvement afforded by this invention over the powder of Example 3, 1812 .parts by weight of the same type powder grains were wet with 145 parts or alcohol and 36 parts by weight of water, which mixture is a poor solvent for ethyl ortho benzoyl benzoate. The

base smokeless powder; however, it is readfly adaptable to the coating or single base powders and the following examples show the improvement obtainable.

( .Exnnms 7 Exulrns 8 To show the improvement possible over the results given in Example 7 a single base powder' was prepared in accordance with this invention m bycoating parts by weight of the powder described in Example 7 by wetting the mass with 10 parts by weight of a 41 alcohol-water mixture and adding thereto 1 part by weight of ethyl ortho benzoyl benzoate. The deterrent is only 7s slightly soluble in liquid. The mass mas tumbled for one hour at 75 C. and finished as in previous examples. The results obtained are listed in the table.

Table Examples '33 age Ex.7 .392 99.0 ELS .921 99.

- duced which sas superior ballistics over prior art powders. .The coating procedure is not time consuming and may be carried out in one step, thus, decreasing labor costs over some of the known methods. I

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

What I claim and desire to protect by Letters Patent is:

1. In theprocess of making progressive burning smokeless powder by coating substantially completely colloided smokeless powder grains with a deterrent material, the improvement comprising wetting the smokeless powder grains with a volatile liquid which is a weak solvent for the deterrent material and substantially a 'non-' solvent for the smokeless powder grains; adding the deterrent material to the wetted smokeless comprising wetting the smokeless powder grains with an alcohol-water admixture which is a weak solvent for the deterrent material and substantially a non-solvent for the smokeless powder grains, the proportion of said alcohol-water admixture being in thQ'OIdBl 01 2:1: adding, as the deterrent r material, symmetrical diethyldiphenolurea to the wetted smokeless powder grains; and tumbling the mass thus formed and heating 'suiliciently to progressively and slowly dissolve small quantities of the deterrent mate- 5 rial in the weak solvent, whereby said small quantities of dissolved deterrent penetrate into the smokeless powder grains to form a uniform deposition thereon which is progressively and a uniformly increased as said deterrent material is progressively dissolved, to form a uniform coating of deterrent on the powder grains.

3. In the process of making progressive burning smokeless powder by coating substantially completely colloided smokeless powder grains with a deterrent material, the improvement com prising wetting the smokeless powder grains with an alcohol-water admixture which is a weak solvent for the deterrent material and substan- I tially a non-solvent for the smokeless powder grains, the proportion of said alcohol-water admixture being in the order of 4:1; adding, as the deterrent material, ethyl ortho benzoyl benzoate Powder grains to form a uniform deposition thereon which is progressively and uniformly increased as said deterrent material is progressively dissolved, to form a uniform coating of deterrent on the powder grains.

4. In the process of making progressive burning smokeless powder by coating substantially I completely colloided smokeless powder grains prising wetting the smokeless powder grains with an alcohol-water admixture which is a weak sol- 4 0 vent for the deterrent material and substantiallya non-solvent for the smokeless powder grains,.

the proportion of said alcohol-water admixture beingin the order of 2:1; adding, as the deterrent material, triphenyl phosphate to the wetted smokeless powder grains and tumbling the mass thus formed and heating sufllciently toiprogressively and slowly dissolve small quantities of the deterrent material in the weak solvent, whereby 60 said small quantities of dissolved deterrent penetrate into the smokeless powder grains to form a uniform depositionthereon which is progressively and uniformly increased as said deterrent material is progressively dissolved, to form a uniform coating of deterrent on the powder grains. 5. The process of claim 1, wherein the volatile liquid is an ethylalcohol-water admixture.

6. The process or claim 1, wherein the volatile liquid is an acetone-water admixture.

'7. The process of claim 1, wherein the-volatile liquid is a dioxane-water admixture.

EILSWORTH B GOODYEAR.

with a deterrent material, the improvement com- 

